1. Field of the Invention
The present invention relates to a breather apparatus provided with a gas-liquid separation chamber for separating oil contents from blow-by gases produced in an internal combustion engine.
2. Description of the Related Art
A gas-liquid separation chamber for separating oil contents from blow-by gases is usually provided on a blow-by gas returning device for retuning blow-by gases leaking from between the pistons and cylinder walls in an internal combustion engine to an intake system for combustion therein so that blow-by gases from which oil has been removed are then returned to the intake system so as to suppress the consumption of oil.
Shown in FIGS. 7 and 8 is an example of an internal combustion engine 01 described in Japanese Utility Model Registration No. 2532890 in which a gas-liquid separation chamber of a type described above is provided within a cylinder head cover which covers a valve system from thereabove.
A valve train 05 is covered with a cylinder head cover 03 which is overlaid on a cylinder head 02 to be joined thereto.
A rectangular opening at a lower end of a side frame wall 04 which forms an upper space within the cylinder head cover 03 is closed with a bottom plate 06 so as to form a gas-liquid separation chamber 07.
A blow-by gas outlet pipe 08 is provided in such a manner as to penetrate through the side frame wall 04, and a blow-by gas inlet port 09 is opened in the bottom plate 06 along a corner portion which is situated away from the blow-by gas outlet port 08.
Then, three bent portions 010 which are each bent to be inclined downwardly are provided at portions along a side edge of the circumferential edge portion of the rectangular bottom plate 06 where the blow-by gas outlet pipe 08 is situated, and a gap 011 through which oil is to be returned is formed in each bent portion 010 between a lower end face of the side frame wall 04 and the bent portion 010.
Blow-by gases in the cylinder head cover 03 flow into the gas-liquid separation chamber 07 through the blow-by gas inlet port 09, and the blow-by gases from which oil contents have been removed are then returned to the intake system through the blow-by gas outlet port 08.
Oil separated from the blow-by gas and collected on an upper surface of the bottom plate 06 flows over the bottom plate 06 which is inclined along the inclination of the internal combustion engine toward the oil return gaps 011, and oil so reaching the gaps flows out through the oil return gaps 011 into the lower space in which the valve train is accommodated.
The oil return gaps 011 are closed with oil which tries to flow out therethrough, so as to prevent blow-by gases present within the cylinder head cover 03 from being blown up into the gas-liquid separation chamber 07 through the oil return gaps 011.
However, in the event that there is little oil flowing out through the oil return gap 011, there may be a case where the gap is not closed with oil, and if this occurs, there may be a case where blow-by gases within the cylinder head cover 03 is blown up into the gas-liquid separation chamber 07 via the gaps 011, resulting in a risk that oil separated from blow-by gases mixes again with the blow-by gases so blown up into the gas-liquid separation chamber to be sent into the intake system.
If the oil return gap 011 is narrowed, the gap 011 can easily be closed with oil, but there may be a case where the gap 011 is rigidly closed with oil due to its viscosity, resulting in a risk that oil is difficult to flow out through the gap 011 before a lot of oil is accumulated on the upper surface of the bottom plate 06.
In addition, there is suggested (in JP-A-10-30423) an example in which an oil flow-down pipe is extended downwardly from a bottom plate constituting a gas-liquid separation chamber, and a lower end of the oil flow-down pipe is formed into an S-shape which faces laterally, whereby the oil flow-down pipe is closed with oil separated from blow-by gases to be collected in a bent portion of the S-shape which faces downwardly. However, this requires the special oil flow-down pipe and complicates the construction, where by the number of components is increased, resulting in a troublesome assembling process.
Additionally, with an oil flow-down pipe of a large diameter, oil does not flow out, and a large amount of oil is accumulated therein, whereas with an oil flow-down pipe of a small diameter, oil accumulated in the oil flow-down pipe is caused to flow back to be easily blown up into the gas-liquid separation chamber due to a negative pressure produced in the intake system.
The oil return gaps 011 are closed with oil which tries to flow out there through so as to prevent blow-by gases present within the cylinder head cover 03 from being blown up into the gas-liquid separation chamber 07 through the oil return gaps 001.
Moreover, once blow-by gases have flowed into the gas-liquid separation chamber 07 through the blow-by gas inlet port 09, a flow of the blow-by gases is formed as indicated by broken line arrows in FIG. 8 which flow is directed over the gas-liquid separation chamber 07 toward the blow-by gas outlet pipe 08.
Therefore, blow-by gases that have flowed into the gas-liquid separation chamber 07 through the blow-by gas inlet port 09 is allowed to act directly on oil accumulated in the oil return gap 011 due to the closure of the gap therewith, and oil is drawn into the blow-by gases to thereby be reversed.
This action makes it difficult for oil to flow out through the oil return gap 011, and if there is only a small amount of oil that closes the gap, the small amount of oil is drawn into the blow-by gases, whereby the gap 011 cannot be closed, resulting in the fact that blow-by gases are easy to be blown up, reducing the gas-liquid separation effect.
The invention was made in view of the drawbacks inherent in the conventional examples, and an object thereof is to provide a breather apparatus for an internal combustion engine which can prevent blow-by gases from being blown up into a gas-liquid separation chamber by closing an oil return port in an ensured fashion without accumulating a large amount of oil separated from blow-by gases in the gas-liquid separation chamber, and further can promote the gas-liquid separation effect with a simple construction.
With a view to attaining the object, according to a first aspect of the invention, there is provided a breather apparatus for an internal combustion engine in which an opening at a lower end of a circumferential wall of a cylinder head cover which defines an internal upper space within the cylinder head cover together with a top wall of the cylinder head cover is closed with a bottom plate so as to form a gas-liquid separation chamber, wherein the bottom plate is inclined when the internal combustion engine is set in a normal posture, further wherein an oil return port is formed at a lowest portion along an edge of a lower side of the inclined bottom plate, further wherein a blow-by gas inlet port is provided at a position along an edge portion of an upper side of the bottom plate which edge portion faces the oil return port, and further wherein a guide wall is provided for guiding flows of blow-by gases that have flowed through the blow-by gas inlet port toward the oil return port such that the flows of blow-by gases are deflected at right angles before the oil return port.
Since the guide wall deflects and guides at right angles the flow of blow-by gases that have flowed in through the blow-by gas inlet port toward the oil return port before the oil return port, the risk is avoided that the flow of blow-by gases acts on oil which is about to flow out through the oil return port to thereby draw oil back into the gas-liquid separation chamber, thereby making it possible to promote the gas-liquid separation effect.
According to a second aspect of the invention, there is provided a breather apparatus for an internal combustion engine in which an opening at a lower end of a circumferential wall of a cylinder head cover which defines an internal upper space within the cylinder head cover together with a top wall of the cylinder head cover is closed with a bottom plate so as to form a gas-liquid separation chamber, wherein the bottom plate is inclined when the internal combustion engine is set in a normal posture, further wherein an oil return port is formed at a lowest portion along an edge of a lower side of the inclined bottom plate, further wherein a blow-by gas inlet port is provided at a position along an edge portion of an upper side of the bottom plate which edge portion faces the oil return port, and further wherein the circumferential wall portion extending along the edge of the lower side of the inclined bottom plate is inclined downwardly toward the oil return port at the lowest portion.
According to the second aspect of the invention, the circumferential wall portion extending along the edge of the lower side of the inclined bottom plate inclines downwardly toward the oil return port situated at the lowest portion, and therefore, oil separated from the blow-by gases can smoothly be led to the oil return port so as to allow oil so led to flow out therethrough, thus the return of oil being facilitated to thereby improve the gas-liquid separation effect.
According to a third aspect of the invention, there is provided a breather apparatus for an internal combustion engine in which an opening at a lower end of a circumferential wall of a cylinder head cover which defines an internal upper space within the cylinder head cover together with a top wall of the cylinder head cover is closed with a bottom plate so as to form a gas-liquid separation chamber, wherein the bottom plate is inclined when the internal combustion engine is set in a normal posture, further wherein an oil return port is formed at a lowest portion along an edge of a lower side of the inclined bottom plate, further wherein a blow-by gas inlet port is provided at a position along an edge portion of an upper side of the bottom plate which edge portion faces the oil return port, and further wherein the oil return port is provided in an expanded portion formed at a position along the edge portion of the lower side of the bottom plate.
According to the third aspect of the invention, since the oil return port is provided in the expanded portion which is formed by being expanded from the edge of the lower side of the bottom plate to be situated at the lower position, the oil return port is allowed to be situated at the lowest position, whereby even if blow-by gases act on oil collected to the periphery of the oil return port, oil is prevented from being reversed by the difference in step between the unexpanded portion along the edge of the lower side of the bottom plate and the expanded portion.
According to a fourth aspect of the invention, there is provided a breather apparatus for an internal combustion engine in which an opening at a lower end of a circumferential wall of a cylinder head cover which defines an internal upper space within the cylinder head cover together with a top wall of the cylinder head cover is closed with a bottom plate so as to form a gas-liquid separation chamber, wherein the bottom plate is inclined when the internal combustion engine is set in a normal posture, and further wherein a recessed portion for holding oil is formed in a lowest portion along an edge of a side of a circumferential edge portion of the inclined bottom plate in such a manner as to straddle the circumferential wall from below so as to form an oil return port, the side constituting a lower side of the inclined bottom plate, whereby a lower end portion of the circumferential wall is brought into contact with oil held in the recessed portion to thereby close the oil return port airtightly.
According to the fourth aspect of the invention, since the recessed portion is formed at the lowest portion along the edge of the side of the inclined bottom plate which constitutes the lower side thereof, oil is allowed to be accumulated in the recessed portion at all times, and since the recessed portion is formed in such a manner as to straddle the circumferential wall from there below so as to form the oil return port, oil collected in the recessed portion overflows to be returned within the cylinder head cover through the oil return port, and blow-by gases from which oil contents are removed are returned to the intake system.
Since the lower end portion of the circumferential wall is brought into contact with oil held in the recessed portion to thereby close the gas-liquid separation chamber with the oil so held, it is possible to prevent blow-by gases within the cylinder head cover from being blown up through the oil return port into the gas-liquid separation chamber 06 together with oil, whereby oil consumption can be suppressed while maintaining high the gas-liquid separation effect.
According to a fifth aspect of the invention, there is provided a breather apparatus for an internal combustion engine according to the fourth aspect of the invention, wherein a portion of the circumferential wall which faces the recessed portion in the bottom plate is extended downwardly such that the extended portion enters oil held in the recessed portion, whereby it is possible to ensure that blow-by gases are prevented from being blown up through the oil return port into the gas-liquid separation chamber 06.
This construction can provide a similar effect to that obtained with the oil flow-down pipe without requiring the same pipe.